At the moment the only way to backup a copy your data for
yourself is to manually use the API. We do have an
exporter in the works, which really won't take us long to
implement. The only real thinking on that is where to put it in the
ui and getting that setup, then we can deploy it to the public. I'd
estimate two weeks before we have that pushed to production.

Engine
Yard sponsors the hosting for Lighthouse, and provides us with
nightly backups of our entire database that we can restore to in
the event of any major disaster.

I don't believe we have any immediate plans of offering an
instant restore option outside using the Lighthouse API to
dump/import/convert your data, as the database is hosted and backed
up on our end.

I'd like to see this feature, as well. Lighthouse is the best
issue tracking system out there, but I've been burned by putting
all my data in one system before and being unable to move about
when the next big thing arrived.

We're looking into the possibilities still as far as how we want
to handle it. Again, Lighthouse has an API, you can retrieve your
data or build your own tool to retrieve your if needs be.
http://lighthouseapp.com/api/ we just dont have an exported built
into the system yet.